Electric assist device for a bicycle

Abstract

An assist device for a bicycle includes a motor, a step-down gear, a free wheel, and a shaft which rotates as one with a right crank and a left crank. The motor transmits an assist torque to the shaft by m the free wheel. The device is designed to be received inside a pedal assembly casing. The shaft is rotatably mounted relative to the casing by two ball bearings. The free wheel includes a plurality of pieces which are placed between the motor and the shaft. The device also includes a torque transmission ring which allows one of the pieces of the free wheel to be secured to the shaft or to one of the cranks. The transmission ring is at least partially placed under one of the two ball bearings.

The invention claimed is: 
     
       1. An assistance device for a bike comprising:
 a motor; 
 a reduction gear; 
 a freewheel; and 
 a shaft rotating solidly with a right crank and a left crank, 
 said motor transmitting an assistance torque to the shaft via the freewheel, 
 said device being configured to be housed inside a bottom bracket shell, 
 said shaft being mounted with the ability to rotate relative to said shell by virtue of two ball bearings, 
 said freewheel being made up of several components which are placed between the motor and the shaft, 
 wherein the device further comprises a torque transmission ring enabling one of the components of the free wheel to be secured to the shaft or to one of the cranks, 
 wherein said transmission ring is at least partially placed under one of the two ball bearings, 
 wherein the torque transmission ring creates a first mechanical connection with one of the components of the free wheel and a second mechanical connection with the shaft or with one of the cranks, 
 wherein at least one of the two mechanical connections can be disconnected in such a way as to remove the shaft, and 
 wherein the transmission ring is positioned in the vicinity of the right crank and the disconnectable mechanical connection is the one between the ring and one of the components of the free wheel. 
 
     
     
       2. The device as claimed in  claim 1 , wherein the free wheel comprises at least one ratchet pawl configured to come into abutment on the teeth of a ratchet wheel and the ratchet wheel is configured to be secured to the transmission ring by splines. 
     
     
       3. The device as claimed in  claim 2 , wherein the transmission ring comprises a splined portion and a portion of frustoconical shape. 
     
     
       4. The device as claimed in  claim 3 , wherein the transmission ring is fixed to the shaft by bonding, shrink-fitting, or radial bind screws. 
     
     
       5. The device as claimed in  claim 3 , wherein the transmission ring comprises a cylindrical portion configured to surround the shaft and a radial arm extending from the cylindrical portion, said radial arm comprising means of blocking with the right crank. 
     
     
       6. The device as claimed in  claim 1 , wherein the shaft and the right crank constitute an independent subassembly that can be disassembled from the device without the need to remove the ball bearings of the device. 
     
     
       7. The device as claimed in  claim 1 , wherein the shaft has a diameter that is substantially constant over its entire length and in that the diameter of the shaft is less than or equal to an inside diameter of the ball bearing placed in the vicinity of the right crank. 
     
     
       8. An assistance device for a bike, comprising:
 a motor; 
 a reduction gear; 
 a freewheel; and 
 a shaft rotating solidly with a right crank and a left crank, 
 said motor transmitting an assistance torque to the shaft via the freewheel, 
 said device being configured to be housed inside a bottom bracket shell, 
 said shaft being mounted with the ability to rotate relative to said shell by virtue of two ball bearings, 
 said freewheel being made up of several components which are placed between the motor and the shaft, 
 wherein the device further comprises a torque transmission ring enabling one of the components of the free wheel to be secured to the shaft or to one of the cranks, 
 wherein said transmission ring is at least partially placed under one of the two ball bearings, 
 wherein the torque transmission ring creates a first mechanical connection with one of the components of the free wheel and a second mechanical connection with the shaft or with one of the cranks, and wherein at least one of the two mechanical connections can be disconnected in such a way as to remove the shaft, 
 wherein the transmission ring is placed in the vicinity of the left crank and the disconnectable mechanical connection is the one between the ring and the shaft or the left crank, and 
 wherein the transmission ring comprises a first portion comprising a tooth set of which each of the teeth is configured to come into contact with a ratchet pawl of the free wheel and a second portion comprising means for blocking the rotation with the left crank or with the shaft. 
 
     
     
       9. The device as claimed in  claim 8 , wherein the rotation blocking means comprise a key. 
     
     
       10. The device as claimed in  claim 8 , wherein the rotation blocking means comprise internal splines configured to collaborate with external splines formed on the shaft.